Strain specific FGF21 expression analysis in wild type (WT) mice and B-hFGF21 mice by ELISA. Serum was collected from WT mice (+/+) and homozygous B-hFGF21 mice (H/H) and analyzed by ELISA with FGF21 ELISA kit. Mouse FGF21 was detectable in WT mice (+/+).Human FGF21 was detectable in homozygous B-hFGF21 mice (H/H). Values are expressed as mean ± SEM.